Presentation Details

Abstract Resume

Background: Archers need to coordinate forearm muscles agonists and antagonists during the shoot. Muscles spanning one joint can coactivate and increase stiffiness to stabilize this
joint. Archery is a sport which needs strength and stability control especially in the forearm and shoulder girdle. Consistency in archery depends on correct posture and adequate muscles activation
during shoot. Central Nervous System controls posture in two actions: Anticipatory Postural Adjustments (APA) and Compensatory Postural Adjustments (CPA) during perturbation. APA is applied to
stabilize the Center of Mass (COM) of body before perturbation, to avoid the risk of imbalance induce by the forecomming perturbation. CPA is reflex response elicited by sensory information and is
also a mechanism to restore COM position in perturbation. Archer positions the bow with one forearm extended, while the other hand push the rope and holds the arrow. These two movements preceed the
arrow release, which perturbes the standing position. Muscle activation in archery remains unclear especially in activation patterns of archers. The objective of study is described activation patterns
of trunk in simulation of competition in archery.
Methods: Eleven archers (5 men and 6 women) of Brazilian Team of Archery participated into this study (21.1±1.4 years old, 6.8±1.5 years of experience). The surface electromyography
(EMG) of several muscles: Pectoralis Major Clavicular Dominant; Upper Abdominal Dominant; Serratus Anterior Dominant; Multifidus Dominant; Latissimus Dorsi Dominant; Trapezius Upper Dominant; Serratus
Anterior Nondominant; Deltoid Posterior Nondominant, electrodes positions in skin preparating occording recommedations in literature (Cram, Kasman & Holtz, 1998). Dominant side is pull the string and
nondominant support the bow. EMG wired data were recorded, filtered, demeaned and rectificed. Sampling frequency was 2 kHz. Accelerometer data set in the fist determined the beginning of the movement,
it is the largest peak in the graph of acceleration by time. Pre-test starting with Maximum Voluntary Contraction. In warm up shoot 3-arrows groups (18 arrows in Warming up). Twelve 6-arrows groups
(each archer has shot 72 arrow to the target) were shot by each archer to target 70 m away. Processed EMG signal divided for CPA, 50 milliseconds-150 milisseconds after clicker. Average and standard
deviation across all subjects and all trials correspond of EMG signal during the CPA.
Results: This study identified that the muscle Multifidus Dominant and Serratus Anterior Nondominant have similar differences in EMG when compare standard deviation. Pectoralis Major
Clavicular, Upper Abdominal Dominant, Serratus Anterior Dominant, Latissimus Dorsi Dominant, Trapezius Upper Dominant and Deltoid Posterior Nondominant present more variability because standard
deviation is bigger than mean for EMG. The activation sequence of the postural muscles expected that other studies may have more intervals for CPA and add APA intervals.
Conclusion: In conclusion is more variability in EMG of CPA data.